<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>javascript 阶段</title>
</head>
<body>

    <script>
        // 数字
        var num = 100;
        // 字符串
        var str = "abc";
        // 做减法运算
        console.log(num - str);
        // NaN 翻译: not a number ,非数字

        // 在开发过程中, 涉及运算的数据,检测其类型是否为number类型

        console.log(NaN === NaN);// false
        console.log(typeof NaN); // number

    </script>
</body>
</html>